British airspace may have been used by the US for the transfer of a prisoner to Syria where he says he was tortured, according to an aviation expert.
Did rendition flights cross UK airspace?
Chris Yates told the BBC the flight carrying Maher Arar must have travelled over airspace controlled by the UK.
Mr Arar, a Canadian, said he wanted European governments to investigate their role in the practice.
In October 2002, Mr Arar was stopped at JFK Airport in New York on his way back home to Canada.
After 12 days he says he was transported on a private jet, eventually arriving in Syria where he says he was tortured.
He told BBC Radio 4's Today programme: "The beating actually started the second day with a black cable. I remember vividly the first hits I got.
"Basically, the interrogator came in the room without even saying anything and he started hitting my palms."
CIA flights have been known to fly over the UK and stop at its airports but it has never been proved that they had prisoners on board.
US federal aviation logs confirm a Gulfstream jet flew the route described by Mr Arar in October 2002.
Mr Yates said: "There is very strong evidence to support the fact that this aircraft passed through UK controlled airspace.
"The aircraft flew from Portland, Maine, to Rome for refuelling. Now that type of aircraft - we are talking about a Gulfstream G3 - has a finite range and it did have an optimum routing for that flight which also took it through the chunk of airspace over the North Atlantic," he said.
He said it would probably have passed through airspace controlled by air traffic controllers at Prestwick, in Scotland.
The Foreign Office says that it would expect the US to seek permission to render detainees through UK airspace.
A freedom of information request shows no Foreign Office inquiries of the US about the flight.
Critics of extraordinary rendition say European governments have consistently turned a blind eye to the practice.
Liberal Democrat leader Sir Menzies Campbell said he believed governments had a legal obligation to make inquiries if it suspected torture was being used.
"What I think is clear is the principle the government has adopted has been what I've described previously as 'hear no evil, see no evil,'" he told Today.
"In particular, there is a legal opinion which says that signatories to the conventions which deal with these matters don't just have a duty to abstain from torture or facilitate torture, they have a duty to investigate if they believe there's any question of torture taking place within their jurisdictions, or the facilitation of torture.
"And of course allowing aircraft either to land or to transit through airspace could in these circumstances be regarded as facilitate."